Someone watching the weekday Mass asked about the prayer I lead afterwards. It is called the Regina Caeli (Queen of Heaven). It is a traditional prayer for the Easter season. The coronavirus makes it even more appropriate this year. Tradition says that back around the year 600 there was a similar plague. Pope Gregory the Great called for a procession through the streets of Rome with an image of the Blessed Virgin, praying for an end to the pestilence. Angels were heard singing the first three lines of the Regina Caeli: “Queen of Heaven, rejoice Alleluia! For he whom you did merit to bear, Alleluia! Has risen as he said, Alleluia!” Pope Gregory added the fourth: “Pray for us to God, Alleluia!” After that he saw a vision of an angel sheathing his sword, showing that the plague was ending. That spot is now called Castel Sant'Angelo. That image of the Virgin Mary still exists, and is called “Mary, Health of the Roman People/Salus Populi Romano.” Pope Francis had that image brought to St. Peter’s Basilica from St Mary Major. Perhaps you saw him praying the Regina Caeli in front of it after the extraordinary Urbi et Orbi blessing in St. Peter’s Square and after the Easter Vigil Mass. You can hear the prayer sung in Latin here: https://www.youtube.com/watch?v=9kZgxYs9lOw. You can read about the image here: https://en.wikipedia.org/wiki/Salus_Populi_Romani.